SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5ef25b3afd13fad009186936cd113cec642b836aee637da84939cbadd97b38b' 
  AND token = 'mWiAuAOPIEqLKRpGTm3MplMh7LzKOpJ2mvJ3675FN+8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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