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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f5cf0b6344552a7100ccf2e81d5ce702bd414030f8380fba66ff1301a16a3a0c' 
  AND token = 'z/2Lo05qCWNRrHCp99FPUIvjIweEFb7xXIB+5FW91Uw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}