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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68ddd3c4b0189959e2e23f26d413a1d03cf7efb8664e0d2e7ac0d6c85c7d8b84' 
  AND token = 'dPBNyz5VZFBNzneQt5OMTFDexf2Mp5VhuBaDVcv51CY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}